How would an open neutral affect a 30 amp service? Are there risks from this for us lowly 30 amper folks?

Depends on where the open neutral is, if it's in the 30 amp rec or anyplace between the rec and your panel you will no have power, if it's in the 240 volt anywhere before the pedestal the voltage on either legs will be floating up an down depending on the load on each leg. So one minute you may have high voltage and the next low voltage.

Depends on where the open neutral is, if it's in the 30 amp rec or anyplace between the rec and your panel you will no have power, if it's in the 240 volt anywhere before the pedestal the voltage on either legs will be floating up an down depending on the load on each leg. So one minute you may have high voltage and the next low voltage.

I would think that #2 and #3 are the same situation. In #2, the neutral and one 50 amp leg are connected to behind the pedestal panel. In #3, the same connection is made in front of the panel by the adapter. If there was only one load in the park all 3 scenarios would give no power, but with other rigs plugged in (or outbuildings, lights, etc.) they will be feeding power from a hot line onto the open neutral, so it can attain pretty much any random voltage between 0 and 240. Even in scenario #1, depending on how the park is wired and where other rigs are plugged in, damage could occur. This is kind of a tough situation to picture all at once, so if I have it wrong, I accept any civil corrections.